Risk mitigation activities for a prototype imaging Fabry-Perot Interferometer (FPI) system, development originating within NASA's Instrument Incubator Program (IIP) for enabling future space-based atmospheric composition missions, are continuing at NASA Langley Research Center. The system concept and technology are focused on observing tropospheric ozone around 9.6 micron, but also have applicability toward measurement of other trace species in different spectral regions and other applications. The latest results from performance improvement and laboratory characterization activities will be reported, with an emphasis placed on testing performed to evaluate system-level radiometric, spatial, and spectral measurement fidelity.